Rivet



Patented Oel. 2, 1945 UNITED STATES PATENT OFFICE ton, Dei., a corporation of Delaware No Drawing. tion Hatch 3l, 1943,

'l Claims. (Cl. ll--50 This invention relates to the production oi' fine denier filaments and multifilament yarns and threads composed of a synthetic linear polymer. More particularly, this invention relates to the production of such filaments. yarns and threads containing incorporated therein a nnely divided. inert material in an amount less than that which will produce a substantially visible delusterins cr dulling eifect. whereby the rupturing of the filaments or yarn. during the cold-drawing thereof, will be materially diminished.

The melt-spinning and cold-drawing (that is, drawing under tension in the solid state) of synthetic linear polymers is weil known in the art. Ihe U. S. patents to Carothers Nos. 2,071,250. 2,071,251, 2,071,253 and 2,130,040 all disclose the melt-spinning and cold-drawing of synthetic linear polymers including poiyamides, polyesters. polyethers and polyanhydrides as well as mixed polymers or interpolymers, for example polyamide-polyesters. Of these polymers. the most interesting and useful are the synthetic linear polyamides. more particularly described in the last two above mentioned patents. It is also well known that other synthetic vlinear polymers, for example vinylidene dichloride polymers, acrylonitrile polymers and interpolymers of vinyl acetate and vinyl chloride can be melt spun and cold-drawn.

The present invention in its broad aspects is applicable to the melt spinning and cold-drawing of any ber-forming synthetic linear polymer.

The cold drawing of synthetic linear polymer yarn is usually done by feeding the yarn from one pair of positively driven rollers to a second pair of positively driven rollers rotating at a suitably higher speed than said first pair. Preferably. the draw tension is concentrated at a. precise point between the pairs of rollers to prevent wandering of the draw-point.

As might be expected, the cold-drawing of yarns composed of fine denier filaments which involves the stretching of the filaments from 200% up to 500%, or more. presents many problems. One of these is the tendency of the filaments and in some cases the entire yarn to break with the consequent production of inferior yarn. As might be expected, this happens more frequently as the filament denier is decreased and as the degree of drawing is increased. In the production oi bright, i. e. substantially undelustered, synthetic linear polyamide hosiery yarn. the breakage of filaments and yarns has been so high as to be a cause of real concern.

It is therefore an object of this invention to produce bright, undrawn. fine denier filaments and multifilament yarns composed of a synthetic linear polymer which can be readily colddrawn without excessive breakage of yarns and filaments.

It is another obiect of this invention to improve the melt spinning of bright, fine denier nlaments and multiillament yarns from a synthetic linear polymer in such a manner as to reduce the breakage of said yarns and filaments in the subsequent cold-drawing thereof,

Other objects of the invention will appear hereinafter.

The objects of the invention may be accomplished, in general, lhy producing bright. colddrawable, iine denier filaments and multifilament yarns composed oi a synthetic linear polymer containing, homogeneously dispersed throughout the body thereof. a nnely divided. inert material in an amount substantially less than that which will produce a visible delustering effect. The preferred procedure for accomplishing this is to prepare a melt oi' a synthetic linear polyamide containing from 0.005% -to 0.05% by weight of the finely divided, inert material, for example titanium dioxide, and melt spinning the polyamide in a known manner.

The addition of finely divided. inert material, for example pigments and pigment-like material. to synthetic linear polymer filament-forming compositions is. of course. well known. Conventionally. this is done to produce opaque or low luster yarns (delustered yarns). With other yarns, it has however also been done for such purposes as to produce staple yarn having good cohesion, or to produce yarn having low running tension in textile equipment.

There is nothing in the above mentioned, previously known processes which would suggest that the addition of less than 0.05% of a finely divided. inert material to a synthetic linear polymer melt will. upon melt spinning. produce tllaments and yarns which can be cold-drawn with decidedly fewer filament and yarn breaks than in the absence of said finely divided, inert material. Buch a minute amount of inert material is definitely insuflicient to accomplish the objects and purposes of the above mentioned, previously known processes` It is known that the presence of finely divided. inert material such as titanium dioxide tends to weaken yarn. It is also known that the colddrawing operation. in view of the high tension employed, is very critical. It would, therefore, be supposed that the cold-drawing cf yam containing such a iinely divided, inert material would result in increased breakage oi' yarns and illaments.

The following speciilc examples are given to -illustrate preferred methods of carrying out the present invention. It is to be understood however that these examples are not to be considered Yas limitative of the scope of the invention.

Example I The yarn was not visibly deiustered.

A similar polyhexamethylene adipamide polymer of relative viscosity 33.5 (determined by the method described below). but containing no titanium dioxide was spun from melt to form a (l-filament yarn. The yarn was subsequently cold-drawn at a draw ratio of 4.40 to produce a 210 denier-60 iliament yarn with a tenacity o! 6.5 grams per denier and an elongation of 14%. In the drawing operation there were 2.0 complete yarn breaks per pound of yarn and a creei mirror test showed forty broken tllarnents per 1.000 yards oi' yarn.

Example Il Poiyhexamethylene adipamide polymer of rela.- tive viscosity 34 (determined by the method described below) and containing 0.05% by weight of titanium dioxide was spun from melt to form a e-nlament yarn which was subsequently colddrawn at adraw ratio or 4.40 to produce a 210 denier-89 iliament yarn with a tenacity or 6.2 vgrains per denier and an elongation of 15%. In the drawing operation there were 0.2 complete yam breaks per pound of yarn. and a creel mirror test showed two broken filaments r 1,000 yards oi' yarn. The yarn was not appreciably deiustered.

A similar polyhexamethylene adipamide of relative viscosity 34 (determined by the method described below). but containing no titanium dioxide was melt spun to form a 69iliament yarn ,which was subsequently cold drawn at a draw ratio oi 4.40 to produce a 210 denier-69 iliament yarn with a tenacity of 6.5 grams per denier and an elongation of 14%. In the drawing operation there were several complete yarn breaks and a creci mirror test showed seventy broken niaments per 1,000 yards of yarn.

A second sample oi the polymer mentioned in the previous paragraph was melt spun to form a Bil-filament yarn. The yarn was subsequently cold-drawn at a draw ratio ot 4.28 to produce a 210 denier-69 iiament yarn with a tenacity ot 5.5 grams per denier and an elongation of 19%. In the drawing operation there were several complete yarn breaks and a creci mirror test showed eightyeight broken iiiamente per 1,000 yards of yarn.

The above two examples show two very im portant advantages which follow the teachings ot the present invention. In the first place, the presence of a small amount o! titanium dioxide in the polymer as spun makes it possible to draw bright yarn without the occurrence. during the the production of a yarn having a higher elongation than would be II) the elongation went up and the tenacity down (which is a well recognised observation in the art), but the draw-twister breaks and broken ends were not decreased. Consequently, the titanium dioxide eil'ect is not a draw ratio eilect. Conversely, it shows that yarn containing small amounts of titanium dioxide can be drawn at a bisher draw ratio to end with the same (desired) elongation and therefore increase the productivity oi' the spinning machines.

While the examples show a preference for a relative viscosity oi' 33.5 to 34.0. the relative viscosity may be between l5 and 80.

The term "relative viscosity as used in this specification is, the ratio oi' absolute viscosity at of the solution of synin 00% formic acid (10% water and fox-mic acid) to the absolute viscosiw at 25 C. (in centlpoises) of the 90% formie acid. An 8.4% (by weight) solution of the synthetic linear polyamides which are com- -il0% iormic acid is used in this determination. Moisture content oi polyamides is disregarded in preparation ronnie acid test solutions spinning and cold-drawing of any liber-forming synthetic linear polymers and is particularly applicable to the melt spinning ot synthetic linear polyamides. Also, although the invention shows its greatest utility in the cold-drawing of melt spun illaments and yarn, it includes in its broader aspects the colddrawing ot polyamide filaments and yarns spun by other methods. e. g. from solution. The invention is substantially limited to momentous structures comprised of tine denier filaments, i. e. less than 20 denier per filament. since such structures are drawn in the atmosphere whereas materially larger filaments are drawn in water and therefore not particularly subject to breaklle.

oxide, calcium sulfate, barium sulfate. kaoiin. (barium sulfate and While it Ls not desired bounded by speculation, it is believed that any inert. discrete, solid. pigment-like particles dispersed in the polymer will result in the same phenomenon. Titanium dioxide is preferred since large quantities of lt 

